Vehicle Test Procedure Adjustments for Tier 3 Certification Test Fuel

The Environmental Protection Agency (EPA) is proposing to make adjustments to certain laboratory tailpipe emission testing procedures for automobiles, light trucks, and heavy-duty pickup trucks and vans as the result of a test fuel change that was finalized as a part of EPA’s 2014 Tier 3 vehicle emissions rule. In that rule, EPA changed its laboratory test fuel to be more similar to typical gasoline currently in use. In the Tier 3 Final Rulemaking, EPA required vehicle manufacturers to perform greenhouse gas (GHG) and CAFE fuel economy testing on the new Tier 3 test fuel, beginning for model year 2020 and later vehicles. Changes to the fuel used for emissions testing can result in a change in emission results on the tests. When we adopted the Tier 3 test fuel, we indicated that we intended to undertake rulemaking to re-align test results from GHG and CAFE fuel economy testing on the new Tier 3 test fuel so they are consistent with test results from testing on the original Tier 2 test fuel, in order to avoid an effective change in the stringency of the GHG and CAFE standards. Specifically, EPA is now proposing adjustment factors to apply to both vehicle GHG and fuel economy test results for the GHG and CAFE programs and the Fuel Economy and Environment Label. In addition, we propose that the shift to required use of the new fuel for all vehicle testing be phased in through Model Year 2024, but required in Model Year 2025. Because the purpose of the rule is simply to realign testing results in response to the test fuel change, there would be no significant costs associated with the proposed action.